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We are aiming at the realization of sub-terahertz LSIs based on ultra high-speed, ultra low-power single-flux-quantum (SFQ) circuits.

We are doing research on several applications as well as a fablication process of high-quality Josephson junctions based on niobium and high-temperature superconductor (HTS). Current subjects are including the following topics:

  • Development of SFQ LSI technology and its application to SFQ microprocessors,
  • Development of an X-ray/THz-wave imaging system using multiple detectors,
  • Development of HTS vertically-stacked Josephson junctions and optical interface,
  • Superconducting quantum computing system using SFQ circuits.

SFQ LSI Technology and Application to SFQ Microprocessors

An SFQ microprocessor prototype, CORE1γ

Large-scale SFQ circuits are essential for their commercialization. We have been developing an SFQ LSI technology in cooperation with Yokohama National University, Superconductivity Research Laboratory (SRL), and National Institute of Information and Communications Technology (NICT).

We have proposed a new logic circuit structure and established a highly frexible, multicast wiring technology. These technologies are used in our latest design of our microprocessor, CORE1γ, which is the largest-scale, most complicated one among the microprocessors developed so far in collaboration with Yokohama National University.

Multiple Detectors System for X-ray/THz-Wave Imaging System

A tested SFQ-ADC including 1st-order decimation filter and its implementation

We have been developing an SFQ analog-to-digital converter (ADC) that has special features of broad band, high sensitivity, high resolution compared to the semiconductor one.

We are now testing the operation of an ADC including SFQ decimation filter and signal processor under an actual X-ray/THz-wave imaging system.

HTS Vertically-Stacked Josephson Junctions and Optical Interfaces

An Optical input interface circuit based on HTS junctions

High-temperature superconductor (HTS) Josephson junctions have high characteristic voltages, applicable to higher-speed SFQ circuits and interface circuits between low- and room-temperature electronics.

We are investigating vertically-stacked Josephson junctions having reduced stray inductances. Characteristic voltage over 2 mV corresponding to 200-GHz operation has been demonstrated, and a double junction with a doubled characteristic voltage has been obtained so far.

We also pursure the optical input and output circuits. We successfully demonstrated 5-GHz optical inputs based on the photomixing technoque.